In general, such a vehicle electronic-equipment system is configured in the form of an aggregate of subsystems including a navigation system; an audio system including a radio and a cassette deck; a compact disk (CD) system; and a mini-disc (MD) system. Each of these subsystems is composed of a single electronic equipment unit, or a unit group including two electronic equipment units, in order to provide a required specific operation.
A manner of mounting the above-described vehicle electronic-equipment system onto a vehicle will be described with reference to FIG. 6. In the illustrated example, an electronic control unit 61 for a navigation system is disposed within a trunk of the vehicle; and a display control unit 62, which communicates with the electronic control unit 61 and displays necessary information on a display, is disposed within an instrument panel 66 of the vehicle, together with an electronic equipment unit 63 for an audio system, an electronic equipment unit 64 for a CD system, and an electronic equipment unit 65 for an MD system.
As schematically shown in FIG. 6, the electronic control unit 61 for the navigation system includes a power supply circuit 61b and a communication control section 61a for communication with other modules. The display control unit 62 includes a communication control section 62a, a power supply circuit 62b, a graphic control circuit 62c for controlling the display (graphics) on the display, and a switch circuit 62d for processing switch input. The electronic equipment unit 63 for the audio system includes a communication control section 63a, a power supply circuit 63b, a radio tuner circuit 63c, a switch circuit 63d, and an audio circuit 63e for amplifying an input signal and outputting an amplified signal.
The electronic equipment unit 64 for the CD system includes a communication control section 64a, a power supply circuit 64b, an audio circuit 64c, a switch circuit 64d, and a mechanical section 64e including a mechanism for driving a CD so as to read information from the CD. Similarly, the electronic equipment unit 65 for the MD system includes a communication control section 65a, a power supply circuit 65b, an audio circuit 65c, a switch circuit 65d, and a mechanical section 65e including a mechanism for driving an MD so as to read information from the MD.
Incidentally, Japanese Patent Application Laid-Open (kokai) No. 2000-95032 discloses a system which is composed of a base unit including an audio equipment control circuit, a switch input circuit, an operation panel, a connector, and a display device; and a plurality of modules which are removably fixed to the base unit. This technique enables free selection and combination of audio equipment units to thereby enable easy upgrading of the system.
However, the electronic equipment units 61 to 65 used in the above-described general system redundantly include functional sections which could be used commonly among the electronic equipment units 61 to 65; e.g., communication control sections 61a, 62a, 63a, 64a, and 65a; power supply circuits 61b, 62b, 63b, 64b, and 65b; switch circuits 62d, 63d, 64d, and 65d; and audio circuits 63e, 64c, and 65c (hereinafter, those sections which can be used commonly among two or more electronic equipment units may be referred to as “control sections”), thereby raising a problem of increased cost. Further, at the time of upgrading or modification of the system, replacement must be performed on a unit-by-unit basis. Therefore, the control section that does not have to be replaced is inevitably replaced, also raising a problem of increased cost.
Meanwhile, the technique disclosed by Japanese Patent Application Laid-Open No. 2000-95032 enables free selection and attachment of modules which are suitable for (adapted to) the audio equipment control circuit contained in the base unit. However, when a unit which is not suitable for the audio equipment control circuit is to be attached, the base unit itself must be replaced with another base unit, resulting in replacement of switches, a display device, etc., which are not required to be replaced. As a result, cost involved in upgrading increases.